1. Field of the Invention
The present invention relates to a portable timepiece in which there is a possibility of the inner pressure of the timepiece exterior assembly being increased as in the case, for example, of a diver's watch suitable for saturation diving.
2. Description of the Prior Art
There is known a diver's watch for saturation diving in which, to cope with a case where the inner pressure of the timepiece exterior case has become higher than the outer pressure thereof, a button of a vent valve provided in the case is artificially depressed, thereby forcibly discharging the gas inside the timepiece exterior case to the exterior of the case (See, for example, JP-A-5-172956).
The vent valve with which this diver's watch is equipped has a stepped hole formed in the case band of the timepiece exterior case, a button, a retaining ring, a coil spring, and packing.
A small diameter hole portion of the stepped hole is open to the inner side of the case band, and a large diameter hole portion of the stepped hole is open to the exterior of the case band. The button has an operating portion fit-engaged with the large diameter hole portion, and a shaft portion extending through the small diameter hole portion. The retaining ring preventing detachment of the button from the stepped hole is connected to the shaft portion inside the timepiece exterior case. The coil spring is accommodated in the large diameter hole portion while fitted onto the shaft portion, urging the button toward the outer side of the case band. The packing is fixed to the shaft portion. In the normal state in which the button is not pushed in, this packing is in contact with the inner surface of the small diameter hole portion or of a pipe attached to this hole portion to exhibit interference; in the state in which the button has been pushed in, it is arranged inside the case band without exhibiting any interference.
Thus, simultaneously with the pushing-in operation of the button, the packing is moved so as to be detached from the small diameter hole portion of the stepped hole into the interior of the case band, and communication is established between the interior and exterior of the case band via the stepped hole. As a result, the gas inside the timepiece exterior case can be discharged to the exterior of this case via the stepped hole.